1. Field of the Invention
The present invention relates to a memory unit for use in an electronic computer and peripheral or terminal equipment thereof.
2. Description of the Prior Art
Generally in an electronic computer or similar apparatus for processing certain data in accordance with a prepared program, it is usual to employ memory units adapted to store and regenerate, when necessary, incorporated program, data inputted to the apparatus, the result of computation and so forth. Such memory units are classified into a variety of types by some fundamentals concerning an internal type or an external type with respect to installation for the computer, capability of reading out or rewriting the data stored, the kind of recording medium used, and the storage system such as magnetic, electric, chemical or mechanical.
As an example of such various memory units, there is known a magnetic disc device disclosed in Japanese Patent Laid-open No. 60-101777. This magnetic disc device functioning as a conventional memory unit comprises, as shown in FIG. 1, a plate-shaped support base 1, a spindle motor 2 mounted as a rotator on the base 1, a disc 3 set on the spindle motor 2 to serve as a recording medium, a head 4 for reading out data from the disc 3 or writing data thereon while being kept in or out of contact with the storage surface of the disc 3, an arm 5 to which the head 4 is attached via a pressure spring 6 joined to the fore end of the arm, a support mechanism 7 for holding the arm 5 firmly on a driving mechanism (not shown) or a stationary mechanism (not shown), and a cover 8 attached to the base 1 to enclose the above-mentioned members.
The configuration of a recording/regenerating circuit means in the magnetic disc device of such entire constitution will now be described below with reference to a block connection diagram of FIG. 2. In the figure, there are shown a flip-flop circuit 9 responsive to a data-clock pulse train a inputted thereto and inverting an output b from a positive (or negative) logic to a negative (or positive) logic by the rise of such data-clock pulse train a; a current control circuit 10 for converting the output b of the flip-flop circuit 9 into a current c and applying the same as a recording current to the head 4; a regeneration amplifying circuit 11 for amplifying the regenerated output d of the head 4 and feeding an output g to a peak detection circuit 12, which inverts an output f from a positive (or negative) logic to a negative (or positive) logic at the peak of the output e of the regeneration amplifying circuit 11; and a one-shot circuit 13 responsive to the output f of the peak detection circuit 12 and triggered by the rise or fall of the output f to feed a positive logic output g to a voltage-controlled variable frequency oscillation circuit (hereinafter referred to as VFO circuit) 14 and AND circuits 15 and 16 merely during a preset time. The VFO circuit 14 receives the output g of the one-shot circuit 13 and oscillates synchronously with the mean phase of the output g within a predetermined time, and the oscillation frequency of the VFO circuit 14 is controlled by a voltage obtained through conversion of the phase difference between the output of the VFO circuit and the output g, in such a manner that the above phase difference is reduced to zero. The output g of one-shot circuit 13 is delayed for a predetermined time, and complementary outputs h and i of VFO circuit 14 are fed to AND circuits 15 and 16 only during a predetermined period of time. In response to the output g of one-shot circuit 13 and the complementary outputs h and i of VFO circuit 14, AND circuits 15 and 16 produce AND outputs j and k respectively. There is further shown a regeneration error detection circuit 17 which receives the logic product outputs j k of AND circuits 15, 16 and produces an output l after detecting any regeneration error.
FIG. 3 is a waveform chart of signals in the individual circuits of FIG. 2, wherein x and y denote times of clock and data pulses respectively, and t denotes a delay time from the output g to the output h.
Referring now to the operation, when the disc 3 is rotated with the spindle motor 2 driven, a floating force is exerted on the head 4 due to a viscous air stream generated on the surface of the disc 3. Such floating force balances with the pressure of the spring 6 applied to the head 4, so that the disc 3 is rotated while a minute space is maintained between the disc 3 and the head 4. When a train of data and clock pulses x, y and a recording instruction are transmitted from the electronic computer to the magnetic disc device in the state mentioned above, a recording current a is caused to flow in the head 4 by the flip-flop circuit 9 and the current control circuit 10, whereby the data is recorded on the disc 3.
Meanwhile, when a regeneration instruction is transmitted from the electronic computer to the magnetic disc device, the regenerated output d of the head 4 is amplified by the regeneration amplifying circuit 11 and, after the peak is detected by the peak detection circuit 12, the train of clock-data pulses x, y recorded on the disc 3 is restored by the one-shot circuit 13. The AND circuits 15 and 16 produce logic product outputs j, k from the train of data-clock pulses x, y or the output g of one-shot circuit 13 and the complementary outputs h, i of VFO circuit 14, and discriminate between a data pulse train y and a clock pulse train x. During regeneration of the data in the magnetic disc device, the regeneration error detection circuit 17 detects any error in the regenerated data and sends a detection signal ( to the electronic computer, which then keeps transmitting an instruction to repeat such regeneration until elimination of the error, thereby obtaining correct data.
However, there exist the following problems in the conventional magnetic disc device of the above-described structure.
Firstly, dust in the magnetic disc device is prone to enter a minute gap between the head and the disc and, when any external great vibration or shock is applied to the disc device, the floating state of the head with respect to the disc is rendered unstable so that the head is finally brought into contact with the disc, whereby the contact surfaces of both the head and the disc are damaged to eventually cause deterioration of the performance or faults in the magnetic disc device.
Furthermore, in relation to the above problem as well, it may happen that the head falls on the disc to induce trouble in case the damaged head is used for a long time, and the data stored on the disc is thereby spoiled. As a result, the work being executed by utilizing the electronic computer and so forth is brought to a halt to consequently bring about operational and economic loss in business.